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Pesticides are usually detected at chronic concentrations (low but persistent) in coastal waters and they can impact non-target organisms, like jellyfish.
The extensive use of pesticides to maximise agricultural production is a consequence of the global increase in the demand for food. Approximately 3.5 million tons of pesticides are used globally every year. Pesticides reach coastal environments through runoff and usually remain at relatively low but persistent concentrations, except after periods of heavy rainfall when the concentrations may spike. Once in the water, pesticides can impact non-target organisms like fish, corals, and even jellyfish.
Once in the water, pesticides can impact non-target organisms like fish, corals, and even jellyfish.
Most jellyfish have different stages in their life cycle (Fig. 1). A swimming medusa produces a larva that settles on a substrate and develops into a polyp (Fig. 2). Polyps are benthic and sessile, which is important because that means they cannot readily move away from a stressor (like the presence of pesticides in the water). The polyps reproduce asexually, producing a swimming ephyra that will grow into a medusa.
Our recent study published in the scientific journal, Environmental Toxicology and Chemistry, investigated the effects of two pesticides, by exposing polyps of the Moon jellyfish, Aurelia aurita, for nine weeks to concentrations of the herbicide atrazine and the insecticide chlorpyrifos that fell within the Australian water quality guidelines. We found that the survival, reproduction and metabolite content (abundance of aminoacids) were not impacted when exposed to the pesticides either individually or in combination.
Our findings suggest that polyps of Aurelia aurita are unaffected by chronic exposure to atrazine and chlorpyrifos pesticides, even on a molecular level. However, we caution against concluding that all jellyfish are robust against pesticides since previous studies on other jellyfish species have observed negative effects on the survival, growth and behaviour.
Future ecotoxicological studies should consider the use of environmentally relevant concentrations of pollutants, or those based on water quality guidelines, as well as the possible interaction between pesticides, to accurately mimic environmental conditions and assess whether water quality guidelines are appropriate.
You can follow the author, Carolina, on Twitter: @JellyfishVibes.